According to May's Glamour, you're "irresistible" to your guy when you blow him while watching TV — just don't swallow, or you might lose that flat belly.
Actually, Glamour isn't explicit about the bloating properties of semen. It does, however, warn against inappropriate breathing. Yes, breathing incorrectly can result in your abdomen "filling up like a balloon" (we thought that was the point), creating a "distended" look. Glamour offers some supposedly slimming breathing tips, but really, why bother with respiration at all? Dispensing with this unnecessary practice will make TV blowjobs easier too!